JPH0528955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a polarizer control circuit for a satellite broadcast receiver that receives a plurality of television signals having different planes of polarization transmitted from a satellite.

BACKGROUND ART Conventionally, satellite broadcasting (television signals) in the 4 GHz band (G band), such as those in the United States, have consisted of two types of signals with vertical and horizontal polarization planes. For example, when 24 channels (3.72 to 4.18 GHz) of television signals are emitted from one satellite, odd channels are sent with vertical polarization planes and even channels with horizontal polarization planes.
(There are also satellites with opposite polarization planes.) Each channel has an occupied band of 40MHz and a CH space of 20MHz, and the polarization plane is switched to prevent interference. A polarizer installed at the focal point of the receiving antenna extracts signals with either vertical or horizontal polarization and transmits them to a low-noise converter (LNB) installed behind the polarizer. FIG. 3 shows the configuration of the above-mentioned satellite broadcasting receiver. In Figure 3, 1 is an antenna, 2 is a polarizer, 3 is an LNB, and 4
a and 4b are the pillars of LNB ₃ and polarizer 2, and pillar 4
Along b, a signal cable, power to the polarizer 3, and control signal transmission line 5 are installed. Reference numeral 6 denotes a support for the antenna 1, and it goes without saying that the elevation angle and direction (eastward or westward) of the antenna 1 can be changed. 7 is a satellite broadcasting receiver, which consists of the following components. 8 is a tuner also called a 2nd mixer, and LNB ₃ converts 24 waves with a center frequency of 3.72 to 4.18 GHz into 24 waves of 970 to 1430 MHz, and tuner 8 tunes to one of the waves. The output of the tuner 8 is an IF frequency of 510 MHz, and the band is, for example, 25 MHz. 9 is a video intermediate frequency amplification circuit (hereinafter referred to as
It is called an IF circuit) and includes a bandpass filter (BPF). 10 is a wideband FM detection circuit, for example, PLL detection is used. 11 is FM detection circuit 1
An audio detection circuit 11 performs FM detection on the audio carrier wave being outputted at 0. The output of this audio detection circuit 11 is converted into an appropriate level and frequency characteristic by an audio signal processing circuit 13 and outputted, and an RF converter 14
The output of the audio signal processing circuit 13 is supplied to. On the other hand, the video signal processing circuit 12 removes high-frequency components of 4.2 MHz or higher and the energy diffusion signal, outputs the signal at an appropriate level, and supplies the output of the video signal processing circuit 12 to the RF converter 14. 15 is an automatic polarization control circuit that changes the plane of polarization and stops it at the optimum point.

An example of the automatic polarization control circuit 15 is shown in FIG.
First, let the desired wave be the N channel. The spectra of the transmitted signals (N-1), N, and (N+1) are
When considering the IF band, the levels are assumed to be equal, as shown in Figure 5A. In this case, the center of the (N-1) channel is 490MHz, and the center of the (N+1) channel is 490MHz.
It shall be 530MHz. The polarization plane of polarizer 2 is
When the signal is approximately halfway between vertical and horizontal, the signal is as shown in Figure 5B.
The output of the IF circuit 9 becomes as shown in FIG. 5C. Assuming that the N-channel signal is vertically polarized, when the plane of polarization of the polarizer 2 becomes vertical, the signal of the adjacent channel drops by about 15 dB, as shown by the dotted line in FIG. 5A. (The degree of separation of the polarizer is
15 dB) Therefore, when it passes through a bandpass waver, the spectrum will be as shown in Fig. 5D.

In the above explanation, the spectrum is illustrated assuming that the FM frequency shift of a normal television signal is about 10 MHz on average. The same applies to each of the following figures. On the other hand, the polarization plane of polarizer 2 and
The relationship between the outputs of the AGC detection circuit 16 is shown by the solid line in FIG. 7A. The AGC detection circuit 16 is the IF circuit 9
generates a DC voltage proportional to the output of the tuner 8, controls the gain of the IF circuit 9 of the tuner 8, and keeps the input and output of the IF circuit 9 constant. That is, AGC is not applied to the IF circuit 9. Therefore, when the plane of polarization becomes vertical and the signal amplitude becomes maximum, the output of the AGC detection circuit 16 becomes maximum. In other words, the polarization plane is changed from the point where the polarization plane of the polarizer 2 (the probe in the case of a polar rotor) is rotated by -45 degrees or more in the horizontal direction from the reference point 0 degrees, that is, from ST in Fig. 7, and the polarization plane is changed horizontally. (-45 degrees), 0 degrees,
If we assume that one sweep of the polarization plane ends at the point where the polarization plane changes vertically (+45 degrees) and goes further beyond the vertical, that is, at END in Figure 7, then under ideal operating conditions, the 7th
It changes as shown by the solid line in Figure A. Similarly, the relationship between the angle of the plane of polarization and the output of the AGC detection circuit 16 when receiving a horizontally polarized signal is shown by the dotted line in FIG. 7A.
The relationship shown by the dotted line or solid line in FIG. 7A is obtained in an ideal state, and the operation at this time will be described with reference to FIGS. 4 and 7A. If the desired wave is N channels, specifying channel N will result in 3-input NOR.
The output of gate 21 goes low, setting flip-flop 20, and its Q output goes high, causing sweep voltage generation circuit 19 to generate a sawtooth voltage or triangular wave. On the other hand, 3 inputs
The output of NOR gate 21 is peak hold circuit 1
7 to discharge the held voltage. As the output voltage of the sweep voltage generation circuit 19 changes, the plane of polarization of the polarizer 2 changes. When a polarizer 2 of a type called a ferrofield is used, the sweep voltage is amplified. In a type of rotor called a polar rotor, the plane of polarization and rotation angle are determined by comparison with the pulse width, so the sweep voltage is converted into a pulse width by the pulse generator 22 and supplied to the polarizer 2. Here we consider Polarota.
By changing the polarization plane from ST in Figure 7A, at +45 degrees,
When the AGC voltage reaches its maximum value, the peak hold circuit 17 holds this peak voltage P _V at its peak. When the pre-sweep pressure reaches END, it changes again in the same way as from ST. At this time, the level comparator 18 compares the output of the AGC detection circuit 16 and the output of the peak hold circuit 17, and when they match, outputs a negative pulse and resets the flip-flop 20. The Q output of the flip-flop 20 becomes low level, the sweep voltage generation circuit 19 no longer generates a sweep voltage, and the DC power for rotating the rotor of the polarizer is no longer supplied from the DC voltage supply circuit 23. (The DC voltage supply circuit 23 supplies DC voltage to the flip-flop 20 only while the Q of the flip-flop 20 is at a high level.)
Therefore, the polarizer of the polar rotor stops at the optimum position of +45 degrees. Next, consider a case where the desired wave is 4 to 5 dB weaker than the adjacent CH. (This kind of situation actually occurs in America.)
When the plane of polarization of the polarizer is between horizontal and vertical, or when there is no polarizer 2, the output side of the tuner 8 has a spectrum as shown in FIG. 6D. At this time,
Assuming that the polarization plane in the previous state was horizontal and now vertical, when the polarization plane of the polarizer does not start to change, the output of the tuner 8 will be as shown in Figure 6A, and after passing through the bandpass waver. However, the spectrum will be as shown in Figure 6D. In such a state, if you start changing the polarization plane from ST, it will look like the dashed line in Figure 7B.
P _H ′ reaches a peak and becomes higher than P _V ′,
Even if P _V ′ is higher than P _H ′, it may reach a peak before the regular P _V . At this time, the output of the tuner 8 becomes as shown in FIG. 6C. When the influence of adjacent waves is small, the solid line or broken line in Figure 7B becomes the 7th line.
The optimum plane of polarization is determined in the same way as in the case of Figure A. It operates as described above when the power is turned on and when a sweep start is manually instructed.

In addition, so-called terrestrial interference is 500MHz, 520M.
If it is around Hz, the influence will cause P _H ,
The AGC voltage becomes maximum at points other than P _V , making it impossible to set the optimal polarization plane.

Problems to be Solved by the Invention However, with the above configuration, the strength and weakness of radio waves,
Due to interference waves, etc., there was a problem in that the following malfunctions often occurred.

(1) Malfunction due to the influence of adjacent channel signals.

(2) Malfunction due to input difference between adjacent channels and desired signal.

(3) Malfunction due to terrestrial interference.

In view of the above-mentioned problems, it is an object of the present invention to provide a polarizer control circuit for a satellite broadcasting receiver that does not cause the above-mentioned errors.

Means for Solving the Problems The present invention solves the above-mentioned problems, and includes: a polarization control circuit that sets a polarizer that selects a polarization plane to an optimal state; and a circuit for determining the state of the polarization plane of the polarizer that supplies a control signal indicating that the polarization plane of the polarizer is in the optimum state,
The configuration is such that the output of a terrestrial interference removal filter inserted after the bandpass filter of the video signal intermediate frequency amplification stage is input to the state determination circuit.

Effects The present invention uses the attenuation characteristics of the terrestrial interference removal filter with the above-described configuration to eliminate the effects of terrestrial interference and adjacent channel signal components, and accurately sets the plane of polarization.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit block diagram of a polarizer control circuit of a satellite broadcasting receiver according to an embodiment of the present invention. In FIG. 1, the same parts as in FIGS. 3 and 4 are given the same numbers. In addition, in the same part of the operation as in the conventional example in the figure, the output of the sweep voltage generation circuit 19 is transferred to the pulse generator 2.
2, it will be the same as the conventional example, so the explanation of the operation of each part other than the sweep voltage generating circuit 19 will be omitted.

In the United States, within the band 3.70 to 4.20MHz, ±10MHz relative to the center frequency of the satellite broadcasting carrier, ₀ .
Terrestrial radio waves may exist at a distance and may be stronger than the TV signal, which may affect the AGC voltage and cause incorrect polarization settings or beats to appear on the screen. (hereinafter referred to as TI filter) is known to be used. In FIG. 1, 29 is a TI filter whose characteristics have a pass band shown in FIG. 2B. In the case of a trap that removes only terrestrial interference waves,
In Figure 2 B, it is possible to have a characteristic that only attenuates by 10 dB only at points 520M and 500M, and does not attenuate the rest, but here,
(In other words, for the center frequency of 510M of the desired wave IF,
Assume that the outside of the range (separated by ±10MHz) is also attenuated as shown in the figure. When the channel designation circuit 31 is operated to designate the N channel, the tuner 8
is tuned to the N channel, so considering the IF band, the spectrum of the desired wave and the adjacent wave is as shown in Figure 2 C.
It will be like this. However, the desired wave is 5 dB weaker than the adjacent wave, the polarization plane of the received wave before the N channel is specified is horizontal, and the N channel is vertically polarized. The vertical and horizontal separation of polarizer 2 is 15 dB. In this state,
The output of the 3-input NOR gate 21 becomes negative due to the pulse from the channel estimation circuit 31, and the flip-flop 20 is set and the Q of the flip-flop 20 is set.
When the output reaches a high level, DC power is supplied from the voltage supply circuit 23 to the polarizer 2, and the sweep voltage generation circuit 19 converts the polarization plane of the polarizer 2 to ST as shown in FIG.
Start the sweep from the voltage that is in phase with . The Q output of the flip-flop 20 is transmitted to the peak hold circuit 17, which discharges the peak hold voltage.
The output of the OR gate 24 is set to a high level, the base of the switching transistor (hereinafter referred to as a transistor) 26 becomes high level through the protective resistor 25, the transistor 26 becomes conductive, and current flows into the coil 27L of the high frequency switching relay 27. flows, contact 2
A short circuit occurs between terminals a and c of 7S. If the characteristics of the bandpass waveform of the circuit 9 are the solid line in Fig. 2A, the transmission characteristics from the tuner 8 to the IF circuit 9 are as follows.
With the addition of the characteristics of the TI filter 29 shown in Figure B,
The characteristics shown in the dotted line in Fig. 2A are obtained, and the tuner 8
Even if the spectrum shown in Figure 2C is obtained with the output of IF
The output of the circuit 9 is as shown in FIG. 2D, and the adjacent peaks P ₀ and P ₂ are attenuated by 15 dB from the peak P ₁ of the desired wave. When a separation degree of 15 dB of the polarizer 2 is added to this and the plane of polarization is set correctly, P ₁ becomes a level 30 dB higher than P ₀ and P ₂ . If the desired wave and the adjacent wave are at the same level at the input of tuner 8, P ₁ will be smaller than P ₀ and P ₂ .
Needless to say, the level will be 35dB higher. In other words, when changing the plane of polarization, the desired wave is 5 dB lower than the adjacent wave.
Even if it is weak, P ₁ is in the output spectrum of IF circuit 9.
Since the level is more than 15dB higher than P ₀ and P ₂ , AGC
Even if the voltage peak point is considered to be the correct plane of polarization after detection, almost no error will occur. That is, a solid line curve (a broken line if the N channel is horizontally polarized) in FIG. 7A is obtained. Even if the polarization planes match when you specify the N channel, if you sweep, the output of the IF circuit 9 will be in the state shown in Figure 2D (the output of the tuner 8 will be the state shown in Figure 2D).
However, since the adjacency does not become any stronger, the peak of the AGC voltage is correctly detected and held.

Next, the polarization plane memory, which is another feature of the present invention, will be described. When the AC on/off circuit 34 is operated to turn on the power, and when the antenna switching circuit 30 is operated to change the angle of the antenna,
The polarization plane control circuit 35 includes a sweep voltage memory 36
and clear 37. Next, when the desired wave (N channel) is specified, the sweep voltage generation circuit 19 generates a sweep voltage as described above. At this time, since the sweep voltage memories 36 and 37 are cleared, the output of the sweep voltage generation circuit 19 is output as is, and the pulse width for controlling the polarizer is changed by the pulse generator 22. At this time, the peak P ₁ of the spectrum of the desired wave at the output of the sweep voltage generation circuit 9 is higher than 15 dB even if it approaches the nearest adjacent wave peaks P ₀ and P ₁ , so the solid line in FIG. A curve is obtained. Next, the sweep of the sweep voltage generating circuit 19 starts again from ST in FIG.
When P _V is reached, flip-flop 20 is reset by the output of level comparator 18 and the sweep voltage of level comparator 19 stops sweeping. The sweep voltage at this time is stored in the sweep memory voltage 36. The sweep voltage can be AD converted and stored as a digital value. Note that the pulse width of the pulse generator 22 at this time may be stored as a digital value. Next, when the X channel is specified, if the X channel is also vertically polarized, the voltage in the sweep voltage memory 36 is read from the polarization plane control circuit 35, transmitted to the pulse generator 22, the pulse width is directly specified, and the polarization is The polarization plane of the device 2 is set vertically, and after the minimum time required for setting the polarization plane (shorter than the sweep time), a signal is sent from the polarization plane control circuit 35 to the level comparator 18, and the level comparator 18 Outputs a coincidence pulse to flip-flop 2
Reset to 0. At this time, the strength of the input signal,
The plane of polarization can be set quickly and accurately regardless of the presence or absence of interference. If the X channel is horizontally polarized, nothing is stored in the sweep voltage memory 37, so the polarization plane control circuit 35 directly transmits the output of the sweep voltage generation circuit 19 to the pulse generator 22.
tell to. Therefore, the characteristic shown by the broken line in FIG. 7A is obtained, and the peak voltage P _H is
In the second sweep, the output of the level comparator 18 becomes low level at the point P _H ,
The flip-flop 20 is reset and the sweep voltage at this time is stored in the sweep voltage memory 37. That is, the polarization plane control circuit 35 includes a flip-flop, a latch memory, a sweep voltage memory 36,
37 write/read control logic and AND OR
consisting of a gate, a sweep voltage memory 36,
It has a function of checking whether data has been written to 37 or not. Furthermore, the polarization plane control circuit 35 can be replaced with a microprocessor. Now, when the sweep voltages for two planes of polarization are stored in the sweep voltage memories 36 and 37, when a channel is specified by the channel specifying circuit 31, the plane of polarization of that channel (determined by the type of satellite, i.e. , determined by the orientation of the antenna) is vertical or horizontal by the polarization control circuit 35,
The voltage value corresponding to P _H or P _V stored in the sweep voltage memory 36 or 37 (not swept) is transmitted to the pulse generator 22 and the probe of the polarizer 2 is rotated to set the plane of polarization to vertical or horizontal. . Therefore, the period during which the Q output of flip-flop 20 is at a high level is shorter than when the sweep voltage generating circuit 19 is swept, and
operates, and the period during which the contact 27S is short-circuited between terminals a and c is also short. Now, when the polarization plane is set correctly, if the terrestrial interference (TI interference) is greater than a certain value, the TI interference detection circuit 28 detects the TI interference, and the TI interference is detected.
The output of the interference detection circuit 28 becomes high level, the transistor 26 becomes conductive, the relay 27 operates, and the contact 27S becomes short-circuited between terminals a and c. Even if the image quality deteriorates to some extent, the broken line in FIG. The video signal in the passband is automatically projected and viewed on the CRT. Furthermore, even if the output of the TI interference detection circuit 28 does not reach a high level, the manual start switch 33
The relay 27 can also be operated by the TI switch.

Note that if the memory values in the sweep voltage memories 36 and 37 are inappropriate, when the manual start switch 33 is operated, the polarization plane control circuit 35 performs the same operation as when changing the antenna, and the sweep voltage memory 3
6, 37, while flipflop 2
0 and the sweep voltage generating circuit 19 performs the sweep operation and control to obtain the characteristics shown in FIG. 7A, as in the case described above.

Effects of the Invention As described above, the present invention can achieve the following excellent effects.

(1) Terrestrial interference can be removed, the influence of adjacent signals can be removed, and the plane of polarization can be set.

(2) When storing the voltage or pulse width for setting the plane of polarization, once the voltage or pulse width is stored correctly, the memory value can be used, so there is no need to narrow the IF band.

(3) The TI interference removal filter and adjacent signal removal filter can be used together.

(4) Except when setting the polarization plane, the IF band can be selected from a sufficiently wide range, so there is no deterioration in image quality.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a polarizer control circuit of a satellite broadcasting receiver according to an embodiment of the present invention, and Fig. 2 is the same.
Characteristic diagram of TI filter, Figure 3 is a block diagram of a satellite broadcasting receiver receiving system, Figure 4 is a block diagram of a conventional AGC voltage peak hold circuit,
5 and 6 are spectral characteristic diagrams for explaining the same operation, and FIG. 7 is a characteristic diagram showing the relationship between the AGC voltage and the angle of the plane of polarization. 2...Polarizer, 16...AGC detection circuit, 17
... Peak hold circuit, 18 ... Level comparator, 19 ... Sweep voltage generation circuit, 20 ... Flip-flop, 21 ... 3-input NOR gate,
22... Pulse generator, 23... DC voltage supply circuit, 24... 3-input OR gate, 25... Protection resistor, 26... Switching transistor, 2
7...Relay, 29...TI filter, 35...
...Polarization plane control circuit, 36, 37...Sweep voltage memory.

[Claims]

1. A color stripe filter is formed by arranging filter strips of three different colors in a fixed order to make one set, and arranging a plurality of sets of filter strips of these three colors in a number equal to or more than the number of display scanning lines of one field of the output video signal. is provided so that the scanning direction of the filter strips is substantially parallel to the longitudinal direction of the filter strips, and one of the output video signals is
an image pickup tube that scans and outputs one set of filter strips of the three colors within a horizontal scanning period; and an output signal of this image pickup tube that is one of the output video signals.
a high-pass reactor wave device that performs high-pass reactor wave processing based on the correlation between a horizontal scanning line and a horizontal scanning line vertically adjacent to the horizontal scanning line; and the three colors in a direction perpendicular to the scanning direction of the image pickup tube. Color demodulation is performed from the color multiplexed signal of each set of filter strips.